Redo how extra emit code flushing operates
The previous implementation of flushEmittedCode(), that flushed on
demand when a process() was encountered, was brittle and susceptible to
mangling the expected sksl when fOut was modified outside of its
control. Given that writeFunction() and generateCode() in the parent
class all do this, it's possible to generate a simple SkSL snippet that
would generate a CPP file that builds invalid final SkSL:
```
in fragmentProcessor child;
bool someGlobalVar = ...;
void main() {
if (someGlobalVar) {
sk_OutColor = process(child, sk_InColor);
} else {
sk_OutColor = half4(1);
}
}
```
The CPP generated code *should* insert 'bool someGlobalVar' at the start
but because of the early flush from the child process and because of
how fOut was overwritten, someGlobalVar's declaration is put into a
stream that is not visible to the flush and ends up being inserted into
the output sksl in an incorrect location (namely after the if condition
that depends on it).
This CL updates the extra emitted code logic to support multiple blocks
of extra CPP code. When a flush point occurs in SkSL writing, a special
token is inserted into the SkSL and a new CPP code buffer is associated
with that token. Then once all of the SkSL is accumulated into the root
output stream, it is processed into sections for each extra CPP block.
Special logic is done so that the SkSL that is emitted before the next
CPP block terminates at the end of the last valid statement before the
special token.
A unit test demonstrating this failure condition is added to SkSLFPTest
and the CL properly passes. Since this bug did not trigger on existing
.fp files, the updated generator does not modify the generated FPs.
Bug: skia:
Change-Id: Ib74911942080f1b964159807a06805bc52898789
Reviewed-on: https://skia-review.googlesource.com/152321
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
3 files changed